1. Technical Field
The present disclosure relates to a method and a system of equalization pre-processing in particular, to a method and a system of equalization pre-processing for sound receiving system.
2. Description of Related Art
As technology advances rapidly, electronic product such as cellular phones, personal digital assistant (PDA), tablet, and laptops have pay more and more attention to the sound quality thereof. In order to fulfill various functionalities of an electronic product while keep pace with the trends of miniaturization, system designers generally shrink the space occupied by acoustic components in the mechanical design. Further, to satisfy different sound quality requirements, various types of acoustic designs, i.e., different waveguide configure design including placement, shape, and length must be done on the electronic product. Accordingly, for a system forming of sound propagating through a waveguide is commonly referred as the sound receiving system.
For example, please refer to FIG. 1, which provides a sectional view illustrating a sound receiving system for a typical condenser microphone. The sound receiving system for condenser microphone 10 includes a microphone unit, a waveguide 101, a plastic rubber 103 for shock absorption and air-tight purposes in system integration, as well as a cloth 105 placed on the microphone unit for dust and water proof application. The microphone unit further includes a cover 107 having sound inlet holes, a ring 109 for forming front cavity, a diaphragm 111 generating acoustic sound through air-squeeze process, a spacer 113, a backplate 115 having a plurality of sound holes, a holder 117, a conductor 119, a backchamber 121, a printed circuit board 127 coupled to the conductor 119, a FET 123 placed on the printed circuit board 127 for amplifying the acoustic signal, and a capacitor 125. Each of these necessary components used for forming the sound receiving system significantly affects the frequency response of the sound receiving (or playing) system, i.e. the sensitivity performance of the sound receiving system. Hence, in general, the sound receiving performance of a microphone unit not only relates to the microphone unit itself but also relates to the design of the associated waveguide. In addition, in order for sound receiving system of a microphone of the electronic product fulfilling the newer wideband voice testing regulations, the waveguide must designed in a way such that the sensitivity response is relatively flat within the frequency range of 100 Hz˜8 KHz.
However, the sensitivity performance of a microphone unit in the sound receiving system would be often over amplified in some frequency band causing distortion in sound signal due to poor sound receiving system design. Furthermore, the sound receiving performance in the current design setting must wait after the mold for the product structure has being developed and obtain through actual measurement. Specifically, since it is in general hard for system designers to acquire the internal structure parameters of the microphone unit from the microphone manufacturer, consequently, system designers are unable to conduct waveguide analysis with unknown internal parameters of the microphone. Therefore the current design for the sound receiving system is basically developed through continuously testing and verifications on different types of new product based on past experience. Then modifies the design accordingly. Consequently, it is very likely to cause delays in product development increasing the development cost while not been able to instantly reflect the demand of customers.